 /*******************************************************************************
  * Copyright (c) 2000, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.expressions;

 import org.eclipse.core.runtime.CoreException;

 /**
  * A property tester can be used to add additional properties to test to an
  * existing type.
  * <p>
  * This interface is not intended to be implemented by clients. Clients
  * should subclass type <code>PropertyTester</code>.
  * </p>
  *
  * @since 3.0
  */
 public interface IPropertyTester {

     /**
      * Returns whether the property tester can handle the given
      * property or not.
      *
      * @param namespace the name space to be considered
      * @param property the property to test
      * @return <code>true</code> if the tester provides an implementation
      * for the given property; otherwise <code>false</code> is returned
      */
     public boolean handles(String namespace, String property);
     
     /**
      * Returns whether the implementation class for this property tester is
      * loaded or not.
      *
      * @return <code>true</code>if the implementation class is loaded;
      * <code>false</code> otherwise
      */
     public boolean isInstantiated();
     
     /**
      * Returns <code>true</code> if the implementation class of this property
      * tester can be loaded. This is the case if the plug-in providing
      * the implementation class is active. Returns <code>false</code> otherwise.
      *
      * @return whether the implementation class can be loaded or not
      */
     public boolean isDeclaringPluginActive();
     
     /**
      * Loads the implementation class for this property tester and returns an
      * instance of this class.
      *
      * @return an instance of the implementation class for this property tester
      *
      * @throws CoreException if the implementation class cannot be loaded
      */
     public IPropertyTester instantiate() throws CoreException;
     
     /**
      * Executes the property test determined by the parameter <code>property</code>.
      *
      * @param receiver the receiver of the property test
      * @param property the property to test
      * @param args additional arguments to evaluate the property. If no arguments
      * are specified in the <code>test</code> expression an array of length 0
      * is passed
      * @param expectedValue the expected value of the property. The value is either
      * of type <code>java.lang.String</code> or a boxed base type. If no value was
      * specified in the <code>test</code> expressions then <code>null</code> is passed
      *
      * @return returns <code>true<code> if the property is equal to the expected value;
      * otherwise <code>false</code> is returned
      */
     public boolean test(Object receiver, String property, Object [] args, Object expectedValue);
 }

